This invention relates to diamines and in particular to substituted diphenylethylenediamines and catalysts derived therefrom. Such catalysts are useful for accelerating asymmetric hydrogenation reactions whose products are useful, for example, as chemical intermediates or reagents for use in the production of fine chemicals or pharmaceutical intermediates.
Catalytic asymmetric hydrogenation involves the activation of molecular hydrogen with chiral metal complexes. However, organic molecules can also be applied as the hydrogen donor in the presence of a suitable chiral catalyst in a process known as transfer hydrogenation. A hydrogen donor such as isopropanol or formic acid is conventionally used with catalysts of the type [(sulphonylated diamine)RuCl(arene)] for the reduction of carbonyl groups. This technology provides a powerful complement to catalytic asymmetric hydrogenation. Transfer hydrogenation, in fact, is particularly suitable for the asymmetric reduction of ketones that are difficult substrates for hydrogenation, such as acetylenic ketones and cyclic ketones.
Heretofore the sulphonylated diamine component of the transfer hydrogenation catalysts has been limited to sulphonylated diphenylethylenediamine (Dpen) and cycloalkyl-1,2-diamines such as 1,2-cyclohexane. For example transfer hydrogenation has been applied using [(tosyl-dpen)RuCl(arene)] catalysts to pharmaceutical products such as 10-hydroxy-dihydro-dibenz-[b,f]-azepines (see WO 2004/031155).
The sulphonylated diamine components used heretofore, while useful, are not equally effective across the range of desirable substrates. Thus, there is a need to expand the range of diamines suitable for use in transfer hydrogenation catalysts that provide catalysts of increased activity, selectivity or stability. We have recognised that, by introducing one or more substituting groups into the phenyl rings of diphenylethylenediamines and by variation of the sulphonate properties, the steric and electronic properties of the diamine component may be usefully adapted.